A Millennium of Snowpack and Glacier Change in Western North America

Summary: In western North America both glaciers and snowpack have declined in recent decades, and further losses are projected through the 21st century. USGS Ecologist Greg Pederson will discuss the uniqueness of the past century of snowpack declines and glacial retreat relative to the past several thousand years in key runoff generating areas of the Colorado, Columbia and Missouri River drainages.

Over the past millennium, late-20th century glacier and snowpack reductions are almost unprecedented in magnitude across the northern Rocky Mountains and in their north-south synchrony across the cordillera. Pederson and his colleagues show both the declines and their synchrony result from unparalleled springtime warming due to positive reinforcement of the anthropogenic warming by decadal variability. The increasing role of warming on large-scale glacier and snowpack dynamics foreshadows fundamental terrestrial and aquatic ecosystem impacts, and declining water supplies across the western U.S.A.